Sky Compass MCP

locate_celestial_object

Determine a celestial object's compass bearing, altitude, and whether it is above the horizon for a given place and time, enabling sky-position checks and tracking.

Instructions

Find a named celestial object's bearing, altitude, and whether it is geometrically above the horizon.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "object_name": "<object_name>"
    },
    "name": "locate_celestial_object"
  }
}

Input Schema

Name	Required	Description
`latitude`	No
`time_utc`	No	ISO 8601 UTC time. Defaults to now.
`longitude`	No
`place_name`	No	Observer place name. An uncached query is sent to public OpenStreetMap Nominatim.
`elevation_m`	No	Elevation above sea level, metres.
`object_name`	Yes	Solar-system body, built-in catalog object, or celestial name/identifier resolvable by SIMBAD, such as 'Andromeda Galaxy' or 'NGC 7000'.
`magnetic_declination_deg`	No	Local magnetic declination, east positive (from a WMM lookup). Bearing = true azimuth - declination.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.0Nov 5, 2026

TDQS

B3.3/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden, and it does disclose one genuinely useful behavioral fact: the horizon check is 'geometrically' based, implying no refraction, terrain, or obstruction modelling. It says nothing about how the observer position is resolved when latitude/longitude, place_name, or neither is supplied, nor about failure behavior for unresolvable names.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense sentence with zero waste, front-loading the action and compressing the three return values into one clause. Nothing is repeated from the schema or padding the text.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter tool that performs external SIMBAD/Nominatim resolution with no annotations and no output schema, the description covers the return shape adequately but leaves the location-resolution contract and network/fallback behavior unexplained. It is enough to attempt a call but not enough to call it correctly in ambiguous cases.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 71% and the schema already documents latitude, longitude, time, place_name, elevation, and the declination-to-bearing relationship, so a baseline of 3 applies. The description adds no meaning beyond the schema and, notably, does not clarify the precedence between place_name and explicit coordinates, which is the highest-risk ambiguity for this tool.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Find a named celestial object') and even previews the outputs (bearing, altitude, horizon flag), so the agent knows exactly what the call produces. It does not distinguish itself from the confusable siblings locate_by_coordinates and track_object, which is the only thing keeping this from a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The sentence is purely a purpose statement; it gives no condition for choosing this tool over locate_by_coordinates (which presumably takes a known position) or track_object, nor any prerequisites such as needing an observer location. With four siblings in an overlapping domain, the absence of routing guidance is a real gap.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server